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T. LENAGHAN AUTOMATIC TELEPHONE SYSTEM Filed April 28, 1920 19 Sheets-Sheet 15 Oct. 30, 1923. 1,472,604

1: LENAGHAN AUTOMATIC TELEPHONE SYSTEM Filed April 28. 1920 19 Sheets-Sheet 16 TWaM HTTOHA/[YS mm 123. wm m T. LENAGHAN AUTOMATIC TELEPHONE SYSTEM Filed April 28, 1920 19 Sheets-Sheet "I F: W535 ATTOR VZYS T. LENAGHAN AUTOMATIC TELEPHONE SYSTEM Filed Apri 1 2,8 1929 19 sheets-sheet 18 Oct. 30, 1923. l941r72fi@4 T. LENAGHAN AUTOMATIC TELEPHONE SYSTEM Filed April 28, 1920, 19 Sheets-Sheet 19 Patented Oct. 30, 1923.

PATENT OFFICE.

THOMAS LENAGHAN, OFIJROYDON, ENGLAND.

AUTOMATIC TELEPHONE SYSTEM.

Application filed April 28, 1920. Serial No. 377,288.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L., 1313.)

To all whom it may concern:

30 it known that I, THOMAS LENAGHAN,

a subject of the King of Great Britain and Ireland, residing at Croydon, in the county I} of Surrey, England, have invented Improvements in Automatic Telephone Systems (for which I have filed applications in Great Britain April 28, 1919, Patent No. 152,702,

and Oct. 2-3, 1919 Patent Numbers 153,167 In and 153,168), of which the following is a specification.

This invention relates to telephone systems and it has for its object to effect certain improvements whereby automatic or semi-automatic operation is obtainable with various advantages such as those hereinafter appearing.

Broadly the invention consists in the employment in a telephone system, of an arrangeinent whereby selectivity of any particular portion of the system is consequent upon the balancing of electrical conditions purposely established at different parts of the system.

More specifically considered, the invention provides for an automatic telephone system in which the wanted groups, trunks and subscribers lines are selected not by their respective position or positions but by the electrical condition or conditions found in the groups, trunks or lines by the seeking member or members temporarily as sociated with the calling line. This is accomplished by associating with each line or group of lines and with each trunk or group of connecting trunks a predetermined artificial electrical condition distinctive to the individual line or roup, that is to say separate from the normal electrical condition of the said group or line, such condition only being available when one'or more of the required lines or trunks is or are disengaged. Associated temporarily with the seeking member or members is. a group of recorders on which are recorded, by the operation of the calling dial, the elec trical conditions of the required'groups and lines, a balancing circuit being connected in proper sequence to the various recorders and to the several seeking members, so that as soon as a seeking member finds a circuit having an electrical condition identical with that imposed upon the seeking member by the recorder, thereby setting up the required balance a relay is released so as to arrest this particular seeking member and extend the circuit to a seeking member in the next group when the succeeding recorder is brought into circuit giving the electrical condition with which the next balance is to be made, and so on until the wanted line is reached.

The setting of the recorders in response to the calling dial movements may be effected as ordinarily or be dependent upon the balancing of a series of electrical conditions extraneous to the normal electrical condition of the line calling that is to say inserted in, or imposed upon the circuit by operation of the dial. Such extraneous electrical condition may be due to resistance, to impedance, to capacity or to any suitable combination thereof.

But in order that the invention may be more readily understood it will now be further described with reference to the accompanying drawings, whereof Figs. 1, 2 and 3 are diagrams chosen to illustrate several ways of carrying out the principle according to which electrical balance is made use of to secure selectivity. Fig. 4 is a diagram of so much of a scheme having a capacity of 280,000 lines, used as hereinafter set forth, as is necessary to understand the description about to be given of a circuit such as is indicated in sketch in Fig. 5. Figs. 6, 6 7 and 7 are four separated portions of a diagram, intended to be united along the lines X Y and Z, illustrating in detail a circuit equivalent to that outlined in Fig. 5. Fig. 6 is a face view and Fig. 6 aside View, to a larger scale, of the dial shown in Fig. .6. Figs. 8 and 8 are diagrams of a recorder and Figs. 9 and 9 the two portions of a diagram of a control repeater hereinafter more particularly referred to. Fig. 10 is a front elevation, Fig. 11 aplan and Fig. 12 a section corresponding to the line XII-XII Fig. 10 of a portion of one form of switch mechanism employed in carrying out the invention. Fig. 13 shows in perspective a detail of Fig. 12. Figs. 14 15, 10, 17 and 18 are diagrams servin to explain the function of the switching mechanism.

Fig. 19 is a diagram illustrating, by way 

